Stabilization of organic substances



STABILIZATION OF ORGANIC SUBSTANCES Joseph A. Chenicek, Long Grove, IlL,assignor to Universal Oil Products Company, Des Plaines, 111., acorporation of Delaware No Drawing. Original application Dec. 19, 1960,Ser.

No. 76,475, now Patent No. 3,189,650. Divided and this application Oct.5, 1964, Ser. No. 401,701

4 Claims. (Cl. 26045.9)

This is a division of copending application Serial No. 76,475, filedDecember 19, 1960, now US. Patent No. 3,189,650, and relates to thestabilization of organic substances by incorporating therein a noveladditive.

Many organic substances undergo undesired deterioration in storage,during transportation or in use due to oxidative reactions and/or due tothe effect of ozone. Illustrative organic substances which undergoundesirable deterioration and may be stabilized in accordance with thepresent invention include gasoline, which may be saturated such asstraight run gasoline, natural gasoline, hydro-reformed gasoline, etc.,or unsaturated gasoline such as thermally cracked gasoline,catalytically cracked gasoline, coker gasoline, polymer gasoline, etc.,or mixtures of saturated and/or unsaturated gasolines, naphtha,kerosene, jet fuel, gas oil, diesel oil, lubricating oil, fuel, oil,residual oil, which may be of petroleum or synthetic origin, grease,rubber, which may be natural rubber or synthetic rubber including SBRrubber, butyl rubber, Buna-N rubber, neoprene rubber, silicone rubber,Thiokol rubber, etc., adhesives, resins, plastics includingpolyethylene, polypropylene, polybutylene, etc., as well as ediblemineral oils and edible and non-edible animal and vegetable fats andoils including lard, beef tallow, soy bean oil, linseed oil, castor oil,menhaden oil, etc., which may be partially or totally hydrogenated orotherwise treated, and solid food products containing the fat or oil.

In one embodiment the present invention is particularly applicable tothe stabilization of rubber which, as hereinbefore set forth, may benatural or synthetic. Such rubber undergoes undesirable cracking due toozone and also undesirable flex cracking, sun checking and otherdeterioration due to oxygen. Such deterioration may be retarded and/ orprevented by means of the novel additive of the present invention. Ashereinbefore set forth, the rubber may be natural or synthetic rubberand may be generally described as as rubbery polymer of a conjugated1,3-diene, either as polymers or as copolymers thereof with otherpolymerizable compounds. Natural rubber includes hevea rubber,caoutchouc, balata, gutta percha, etc. Much of the synthetic rubber nowbeing produced commercially is known in the art as SBR rubber and is acopolymer of styrene and butadiene Other synthetic rubbers have beenhereinbefore set forth.

The present invention also is particularly applicable to thestabilization of gasoline in order to retard and/or prevent gumformation, discoloration and other deterioration of the gasoline.

The novel additive of the present invention is N,N'- bis (1,3 dimethyl 3methoxybutyl) p phenylenediamine. This additive is very effective inpreventing deterioration of organic subtsances and particularly ofrubber and gasoline as hereinbefore set forth. The novel additive of thepresent invention is a solid at room temperature and accordingly offersnumerous advantages in handling, transporting and using. For example, inthe compounding of rubber, manufacturers prefer to work with solidingredients. Because the compounder primarily handles solid ingredients,this available equipment is particularly suited for the weighing,handling and com- I United States Patent "ice pounding of the solidingredients. Accordingly, many compounders find advantages in workingwith solid additives.

Another advantage of the additive of the present invention relates toits use in gasoline. At the present tune a particularly effective andextensively used antioxidant in gasoline isN,N'-di-sec-buty1p-phenylene-diamine. This antioxidant is marketed as aliquid and also is classified as toxic and accordingly must be handledwith care. In contrast, the additive of the present invention is a solidand is considerably less toxic. Accordingly, there is less hazard to thepersonnel working with this additive.

In one embodiment the present invention relates to a method ofstabilizing an organic substance normally subject to deterioration whichcomprises incorporating in said organic substance a stabilizingconcentration of N,N bis (1,3- dimethyl 3 methoxybutyl) pphenylenediamine.

In a specific embodiment the present invention relates to a method ofstabilizing rubber normally subject to cracking due to ozone whichcomprises incorporating in said rubber from about 1% to about 5% byweight of N,N bis (1,3 dimethyl I l-methoxybutyl) p phenylenediamine.

In still another specific compound the present invention relates to amethod of stabilizing gasoline normally subject to oxidativedeterioration which comprises incorporating in said gasoline from about0.000l% to about 1% by weight of N,N bis (1,3 dimethyl 3 methoxybutyl-p-phenylenediamine.

In still another embodiment the present invention relates to an organicsubstance normally subject to deteriora tion containing a stabilizingconcentration of N,N-bis 1,3 dimethyl-3 methoxybutyl)-p-phenylenediamine.

As hereinbefore set forth, the novel additive of the present inventionis N,N' bis (1,3 dimethyl 3- methoxybutyl)-p-phenylenediamine. Althoughthis compound may be prepared in any suitable manner, a particularlypreferred method is by the reductive alkylation of p-phneylenediamine,p-nitroaniline and/or l,4-dini-' trobenzene with4-methyl-4-methoxy-2-pentanone. The reductive alkylation may be effectedin any suitable manner. A suitable catalyst for effecting the reactioncomprises a mixture of the oxides of chromium, cobalt and bariumalthough other suitable catalysts may be employed. Other catalystsinclude those containing cobalt, nickel, platinum, molybdenum, etc. Ingeneral, the reaction is effected at an elevated temperature of fromabout 200 to about 500 F. and a hydrogen pressure of from about 50 toabout 3000 pounds per square inch.

As hereinbefore set forth, the preferred additive of the presentinvention is N,N'-bis-(1,3-dimethyl-3-rnethoxybutyl)-p-phenylenediamine.In another embodiment, the novel additive isN-(l,3-dimethyl-3-methoxybutyl)-N- R-p-phenylenediamine in which R isselected from the group consisting of alkyl, aralkyl, aryl, alkaryl andcycloalkyl. In this embodiment at least one substituent attached to anitrogen atom must be a 1,3-dimethyl-3- methoxybutyl substituent.Compounds in which R in the above formula is aryl are preferred in thisembodiment and include compounds as N-(l,3-dimethyl-3-methoxybutyl)-N-phenyl-p-phenylene-diamine, N(1,3-dimethyl-3-methoxybutyl)-N'-tolyl-p-phenylenediamine, N- (1,3dimethyl 3 methoxybutyl) N xylyl pphenylenediamine, N-( 1,3-dimethyl-3-methoxybutyl -N- ethylphenyl-p-phenylenediamine,N-(l,3-climethyl-3 methoxybutyl)-N'-propylphenyl p phenylenediamine, N-(1,3 dimethyl 3 methoxybutyl) N butylphenylp-phenylenediamine, etc.Other illustrative compounds in which R is selected from alkyl, aralkyl,alkaryl and cycloalkyl include N (l,3-dimethyl-3-methoxybutyl) N- aisopropyl-p-phenylenediamine, N-(1,3 dimethyl 3 methoxybutyl-N'-sec-butyl-p-phenylenediamine, N-( 1,3-dimethyl-3-methoxybutyl)-N'sec pentyl p phenylenediamine, N-( l,3-dimethyl-3-methoxybutyl-N-sec-hexyl-pphenylenediamine, N-( 1,3-dimethyl-3-methoxybutyl) -N'-sec-heptyl-p-phenylenediamine, N-(1,3-dimethyl 3 methoxybutyl)N'-sec-octyl-p-phenylenediamine, N- (1,3-dimethyl-3-methoxybutyl)-N-sec-nonyl p phenylenediamine, N-(l,3-dimethyl-3-methoxybutyl) -N'-sec-decyl-pphenylenediamine, N-1,3,-dimethyl-3-methoxybutyl) -N'- sec-undecyl-p-phenylenediamine,N-(1,3-dimethyl 3 methoxybutyl)-N'-sec-dodecyl-p-phenylenediamine, etc.,N- (1,3 dimethyl 3 methoxybutyl) N benzyl pphenylenediamine, N-(1,3-dimethyl-3-methoxybutyl) -N'- phenethyl-p-phenylenediamine,N-(1,3-dimethyl 3 metoxybutyl -N-phenpropyl-p-phenylene diamine,N-(1,3-dimethyl 3 methoxybutyl) N phenbutyl p phenylenediamine, N(1,3-dimethyl-3-methoxybutyl)-N'-phenpentyl-p-phenylenediamine, N(1,3-dimethyl-3-methoxybutyl) N-phenhexyl-p-phenylenediamine, N (1,3dimethyl 3 methoxybutyl) N' phenheptyl p phenylenediamine,N-(1,3-dimethyl-3-methoxybutyl)-N phenoctyl-p-phenylenediamine, etc.,N-(1,3-dimethyl 3 methoxybutyl)-N'-cyclopentyl-p-phenylenediamine, N(1,3- dimethyl 3 methoxybutyl)-N-cyclohexyl-p-phenylenediamine, etc. Itis understood that the various compounds in this embodiment of theinvention are not necessarily equivalent but all of them will beeffective in stabilizing rubber and other organic substrates.

As hereinbefore set forth, the novel additive of the present inventionis used as an additive to retard and/or prevent deterioration of organicsubstances. The additive is used in a small but suflicient concentrationto obtain the desired stabilization, which concentration generally iswithin the range of from about 0.000l% to about 5% by weight, dependingupon the specific organic substance being stabilized. For example, whenused in rubber, the additive generally is utilized in a concentration offrom about 1% to about 5% by weight of the rubber hydrocarbon. When usedin gasoline or other hydrocarbon distillates or fatty materials, theadditive is used in a concentration of from about 0.0001% to about 1% byweight thereof. When desired, the additive of the present invention maybe prepared as a physical mixture with one or more other solid additivesto be incorporated in the specific organic substrate being stabilized.

It is understood that the additive may be incorporated in the organicsubstance in any suitable manner. For example, when incorporated in aliquid organic substance, the additive is added to the liquid and thenpreferably is suitably agitated to obtain uniform distribution therein.When the additive is incorporated in a compounded substrate, theadditive may be mixed with one or more of the ingredients and thenprocessed therewith into the final composition or the additive may beincorporated as a final step in the compounded material. For example,when the additive is to be incorporated in rubber, it may be addedeither alone or with one or more of the other ingredients and compoundedin this manner into the mix prior to vulcanization thereof. In anotherembodiment the additive may be applied in the form of dust or spray ontovulcanized rubber products. As another example, when the additive is tobe incorporated into grease, it may be mixed with one or more of theingredients prior to final compositing into the grease product.

It is understood that the additive of the present invention may be usedalong with other additives incorporated in the organic substances. Forexample, when used in rubber, the additive in the present invention maybe used along with other antioxidants such as phenyl-betanaphthylamine,6-phenyl-2,2,4-trimethyl-1,Z-dihydroquinoline, marketed under the tradename of Santoflex-B, 2,2'-methylene-bis-(4-methyl-6-tert-butylphenyl),2,6 ditert-butyl-p-cresol, the reaction product of acetone anddiphenylamine, marketed under the trade name of B.L.E., etc. Theseantioxidants generally are used in a concentration from about 0.5% toabout 3% by weight of the rubber. Also, the additive may be used alongwith parafiin and/or microcrystalline wax, these generally being used ina concentration of 0.5% to about 3% by weight of rubber.

It is understood that the rubber which is stabilized in accordance withthe present invention includes rubber used for automobile tires andtubes, hose, belting, sheet and thread rubber, rubberized fabrics,molded goods, boots and shoes, etc., whether vulcanized in a mold, inopen steam, in hot air, or in the cold by the so-called acid process.

The following examples are introduced to illustrate further the noveltyand utility of the present invention but not with the intention ofunduly limiting the same EXAMPLE I N,N' bis-(1,3-dimethy1-3-methoxybutyl)-p-phenyleneamine was prepared by thereductive alkylation of p-phenylenediamine with4-methyl-4-methoxy-2-pentanone. The preparation was made as follows: 108grams of p-phenylenediamine, 650 gramsof 4-methyl-4-methoxy-2-pentanoneand grams of a platinum-alumina catalyst containing approximately 0.4%by weight of platinum were supplied to a rocking autoclave, which thenwas pressured with atmospheres of hydrogen and heated to 320 F. Thereaction at this temperature was continued for 6 hours, after which theautoclave was cooled and the products were withdrawn, filtered to removethe catalyst and then distilled on a steam bat at 50 mm. pressure toremove excess ketone. 280 grams of a light colored crystalline solidwere recovered, the solid having a melting point of 176 F. The solid wasanalyzed and found to have a nitrogen equivalent of 174 whichcorresponds to the theoretical nitrogen equivalent of 168 forN,N'-bis-(1,3- dimethyl-3 -methoxybutyl -p-phenylenediam1ne.

EXAMPLE II N,N'-bis-( 1,3-dimethyl-3-methoxybutyl -p-phenylenediamine isused as an inhibitor in a gasoline comprising a blend of eatalyticallyreformed and catalytically cracked gasolines. The gasoline withoutinhibitor has an induction period of 240 minutes. Upon the addition of0.002% by weight ofN,N-bis-(1,3-dimethyl-3-methoxybutyl)-p-phenylenediamine to anothersample of the gasoline, the induction period of the gasoline isincreased to 473 minutes.

EXAMPLE III N,N'-bis- 1,3-dirnethyl-3-methoxybutyl) -p-phenylenediamineis used as an antiozonant in SBR rubber. 2.5% by weight ofN,N'-bis-(1,3-dimethyl-3-methoxybutyl)-pphenylenediamine is incorporatedin a commercial rubbery composition containing the usual ingredientsincluding carbon black, zinc oxide, sulfur, etc. The ingredients arecombined on a rubber mill in the conventional manner and then themixture is cooled.

A sample of the rubber without additive and a sample of the rubbercontaining N.N'-bis-(1,3-dimethyl-3-methoxybutyl)-p-phenylenediamine maybe evaluated in a number of different ways to determine the effect ofozone on the rubber. In one method the samples of the rubber are cut instrips of 1 inch by 4 inches and then evaluated either in indoor oroutdoor exposure tests. In the indoor test, the rubber samples areelongated and mounted on varnished wooden panels, after which they areinserted in an ozone cabinet and exposed to an atmosphere containing 50parts of ozone per 100 million parts of air at [00 F. In the outdoorexposure tests, the strips of rubber are bent double and mounted on aboard and then samples are exposed to outdoor weather.

When evaluated by both of the methods outlined above, the samples ofrubber containing N,N-bis-(l,3-dimethyl-3-methoxybutyl)-p-phenylenediamine resists cracking due to ozone for aconsiderably longer period of time than the 2 hours for the sample ofrubber without additive in the ozone cabinet and the less than one weekfor the sample of rubber without additive in the outdoor exposure testbefore the occurrence of first crack inthese samples.

EXAMPLE IV Because the product prepared as described in Example Icontains two asymmetric carbon atoms separated by a plane of symmetry,it is expected that the product would be separable into two isomershaving different melting points. Accordingly, a product prepared in themanner described in Example I was subjected to fractionalcrystallization by extraction in pentane-acetone solvent and twofractions were recovered, one melting at 140 F. and the other melting at225 F. These fractions were analyzed and found to have nitrogenequivalents of 167 and 169, respectively, which correspond to thetheoretical nitrogen equivalent of 168.

EXAMPLE V The isomer having a melting point of 140 F. was evaluated asan antiozonant in SBR rubber having the following recipe:

1 N-cyclohexyl-2-benzo'thiazolesulfenamide.

The rubber was cured for 40 minutes at 284 F. and then was cut into teststrips of 1 inch by 4 inches. The test strips Were elongated in oneseries and in another series and then mounted on varnished Woodenpanels. The panels were placed in an ozone cabinet and subjected to anatmosphere containing 50 parts of ozone per 100 million parts of air at100 F. and the time to first crack is noted. The results of theseevaluations and of a control sample of the rubber (not containing theantiozonant) are reported in the following table:

Table II Huors to First Crack Concentration of Antiozonant,

Percent by Weight 10% Elongation 20% Elongation It will be seen that thesample of rubber not containing the antiozonant underwent cracking inless than 1 hour. On the other hand, the samples of rubber containingthe antiozonant of the present invention were considerably improved.

EXAMPLE VI The isomer having a melting point of 225 F. and recovered asdescribed in Example IV also was evaluated in SBR rubber in the samemanner as described in Example V.

The results of these evaluations are reported in the following table:

Here again it will be noted that the antiozonant in the presentinvention was very effective in retarding cracking of the rubber.

EXAMPLE VII The isomer melting at 225 F. and recovered as described inExample IV also was evaluated in a heavy duty natural rubber of thefollowing recipe:

1 N-cyclohexyl-2-benzothiazolesulfenamide.

The rubber preparations were processed in the conventional manner, outinto strips and evaluated in the same manner as described in Example V.The results are reported in the following table:

Table V Hours to First Crack Concentration of Antiozonant, Percent byWeight 10% Elongation 20% Elongation None -1. 5 1 4 168 168 5 168 168The hours to first crack reported above relate to surface cracks. In thecase of the samples of rubber containing 4% and 5% by weight,respectively, of the antiozonant, edge cracks were noted at about 40hours in the samples which were elongated 20% and 168 hours in thesamples which were elongated 10%. Thus it will be seen that theantiozonant was very eifective in stabilizing the rubber againstcracking.

EXAMPLE VIII N,N' bis (1,3 dimethyl-3-methoxybutyl)-p-phenylenediamineis used as an antioxidant in synthetic lubricating oil. The syntheticlubricating oil is dioctyl sebacate and the antioxidant is incorporatedtherein in a concentration of 1% by weight. The dioctyl sebacate then isutilized as a lubricant in high temperature service. This additiveserves to prevent oxidative deterioration of the lubricant during suchuse as determined by analyses of the used oil. These analyses includedetermination of the Induction Period (hours to 5 pound pressure drop)according to ASTM Method D942 and also the percent insoluble inisooctane and the percent change in viscosity.

EXAMPLE 1X N,N' bis (1,3 dimethyl-3rnethoxybutyl)-p-phenylenediamine isused as an additive in lithium base grease. The grease is prepared bymixing 91% of a Pennsylvania bright stock with 8% of lithium stearate.The mixture is heated at about 450 F. with agitation. Subsequently, thegrease is cooled to 320 F. while agitating and, at this temperature, 1%by weight of N,N'-bis-(1,3-dimethyl-3- methoxybutyl)-p-phenylenediamineis added. Agitation is continued and the mixture then is cooled to about250 F. and the grease then further cooled slowly to room temperature.

The stability of the grease is tested according to a modified NormaHoffman method in which a sample of the grease is placed in a bomb inthe presence of brass discs acting as an oxidation catalyst, and oxygenis charged thereto. The bomb then is heated to 212 F., and the timerequired for a drop of five pounds pressure is taken as the InductionPeriod. When so evaluated, a control sample of the grease (notcontaining this additive) has an induction period of 1-0.5 hours. On theother hand, the Induction Period of the sample of grease containing 1%by weight of N,N-bis-(1,3-dimethyl-3-methoxybuty1)-pphenylenediamine isconsiderably increased.

I claim as my invention:

1. A rubbery polymer of a conjugated 1,3-diene normally subject todeterioration due to ozone containing a stabilizing concentration ofN-(1,3-dimetl1yl-3-methoxybutyl)-N'-R-p-pheny1enediamine where R isselected from the group consisting of alkyl, aralkyl, aryl, alkaryl andcycloalkyl.

2. A rubbery polymer of a conjugated 1,3-diene normally subject tocracking due to ozone containing from about 1% to about 5% by weight ofN,N'-bis-(1,3-dimethyl-3-rnethoxybutyl)-p-pl1enylenediarnine.

3. A rubbery polymer of a conjugated 1,3-diene normally subject tocracking due to ozone containing a stabilizing concentration ofN,N-bis-(1,3-dimethyl-3-methoxybutyl)-p-pheny1enediamine.

4. A rubbery copolymer of butadiene and styrene containing a stabilizingconcentration ofN,N'-bis-(1,3-dimethyl-3-methoxybuty1)-p-phenylenediamine.

References Cited by the Examiner UNITED STATES PATENTS 2,684,893 7/1954Hughes et a1 260-573 2,797,152 6/1957 Hughes et a1 260-573 2,867,6041/1959 Rosenwald et a1. 260577 DANIEL E. WYMAN, Primary Examiner.

1. A RUBBERY POLYMER OF A CONJUGATED 1,3-DIENE NORMALLY SUBJECT TODETERIORATION DUE TO OZONE CONTAINING A STBILIZING CONCENTRTION OFN-(1,3-DIMETHYL-3-METHOXYBUTYL)-N-R-PHENYLENEDIAMINE WHERE R IS SELECTEDFROM THE GROUP CONSISTING OF ALKYL, ARALKYL, ARYL, ALKARYL ANDCYCLOALKYL.